SQL无效标识符....？

Question

我想在OrderDetail中将订单100的产品121的价格更改为7.50美元

我收到此错误代码

SQL> UPDATE OrderDetail_mys
  2    SET ProductPrice = 7.50
  3  WHERE ProductID = 121;
  SET ProductPrice = 7.50
      *
ERROR at line 2:
ORA-00904: "PRODUCTPRICE": invalid identifier 

OrderDetail的SQL表

CREATE TABLE OrderDetail_mys (
 OrderID    NUMBER(3)       NOT NULL,
 ProductID  NUMBER(3)       NOT NULL,
 ProductQty NUMBER(4)       NOT NULL,
 ProdcutPrice   NUMBER(6,2)     NOT NULL,
 PRIMARY KEY    (OrderID, ProductID),
 FOREIGN KEY    (OrderID)   REFERENCES Order_mys,
 FOREIGN KEY    (ProductID)     REFERENCES Product_mys
 ) ;